Developments of Electrolyte Systems for Lithium–Sulfur Batteries: A Review

Abstract

With a theoretical specific energy five times higher than that of lithium-ion batteries (2,600 vs.~500Wh kg −1 ), lithium-sulfur (Li-S) batteries have been considered as one of the most promising energy storage systems for the electrification of vehicles. However, both the polysulfide shuttle effects of the sulfur cathode and dendrite formation of the lithium anode are still key limitations to practical use of traditional Li-S batteries. In this review, we focus on the recent developments in electrolyte systems. First, we start with a brief discussion on fundamentals of Li-S batteries and key challenges associated with traditional liquid cells. We then introduce the most recent progresses in liquid systems, including ether-based, carbonate-based, and ionic liquid-based electrolytes. And then we move on to the advances in solid systems, including polymer and non-polymer electrolytes. Finally, the opportunities and perspectives for future research in both the liquid and solid Li-S batteries are presented.

Rechargeable Magnesium–Sulfur Battery Technology: State of the Art and Key Challenges

“…Overall, the opening circuit voltage in the Mg–S batteries lies around 1.8 V. During its entire discharge reaction, Mg–S batteries based on an S 8 cathode can be operated between 0.4 and 1.8 V, where the discharge plateaus are at 1.6 and 1.0 V, respectively, resulting in a specific discharge capacity of 800 mAh g −1 sulfur . In comparison, the initial discharge process in rechargeable Li–S batteries can take place between 1.0 and 3.0 V, with two discharge plateaus at 2.4–2.1 and 2.1–1.5 V, respectively, resulting in a higher theoretical gravimetric energy density around 1000 mAh g −1 sulfur , but a lower volumetric energy density of 2062 mAh cm −3 compared to the one of Mg–S batteries (3832 mAh cm −3 , vide supra). In addition, unlike in the Li–S system, where the lithium polysulfides have similar stability and are all redox‐active, the discharge products from Mg–S batteries, Mg 3 S 8 and MgS, were found to be highly stable, which significantly impedes and often stops recharging of the batteries …”

High‐Energy, High‐Rate, Lithium–Sulfur Batteries: Synergetic Effect of Hollow TiO2‐Webbed Carbon Nanotubes and a Dual Functional Carbon‐Paper Interlayer

“…For example, the insulating character of sulfur (S 8 ) and lithium sulfi de (Li 2 S) impede the full electrochemical utilization of sulfur. [43][44][45][46] Inspired by the previous work where the Naalginate binder was used to stabilize the sulfur electrode, [47][48][49][50] we selected the chitosan binder in our electrode formulations in order to reduce the electrode volume expansion and loss of active material caused by dissolved lithium polysulfi des. [11][12][13][14] Other issues such as low Coulombic effi ciency, high self-discharge, and huge volume change remain unsolved.…”

Chitosan as a functional additive for high-performance lithium–sulfur batteries

“…Fig.1a shows the discharge curves of the batteries utilizing the cathode with chitosan. During the discharge, there are two separate plateaus representing two complete reduction reactions [2]. The upper discharge plateau at 2.3 V corresponds to the reduction reaction from sulfur (S 8 ) to long-chain polysulfide (Li 2 S x , 4 < x ≦ 8).…”